hotato 0.7.1

Fixed

• hotato contract unpack --force no longer deletes the existing output
  directory before the archive has proven valid. In 0.6.0 and 0.7.0, a
  corrupt or hostile archive combined with --force destroyed the
  directory the user asked to replace and then failed. The destination is
  now touched only on the success path, after every guard and the full
  extraction into the temporary directory have passed. Found by external
  diligence against the published package; regression-tested with the
  exact reproduction.